A stoker-type incinerator is an incinerator including a stoker formed by fire grates at a fixed stage and a movable stage being alternately arranged. In the stoker-type incinerator, while waste (object to be burned) put in by a hopper is stirred and moved forward, waste in a drying zone disposed on the upstream side of the stoker is dried by reciprocating the movable stage using a hydraulic device. The stoker-type incinerator is configured such that main combustion is performed while primary combustion air is put in a next main combustion zone of the drying zone and ember combustion is performed on combusted residues in an ember combustion zone on the most downstream side.
In such a stoker-type incinerator, a technique of allowing recirculated exhaust gas in which part of combustion gas (exhaust gas) in a combustion gas channel on the upper side of a stoker is extracted to reflux to a secondary combustion chamber in the combustion gas channel through a recirculation passage and providing the recirculated exhaust gas together with secondary combustion air for combustion is provided (for example, see PTL 1).
In other words, in this stoker-type incinerator, a furnace exhaust gas recirculation system is employed as one of means for achieving stabilized combustion with a low air ratio (reduction in exhaust gas flow rate of a furnace outlet). The furnace exhaust gas recirculation system is a system which draws combustion exhaust gas in a combustion region, boosts the combustion exhaust gas using a fan or the like, and then puts the combustion exhaust gas into a region of a secondary combustion unit again, because combustion exhaust gas generated from an ember combustion zone does not almost consume oxygen and has a composition close to the composition of air. Further, the furnace exhaust gas recirculation system is a system of improving boiler efficiency and achieving miniaturization of an exhaust gas treatment system by means of realizing stabilized combustion with a low air ratio and reducing the exhaust gas flow rate of the furnace outlet.